A global trend in belowground carbon allocation: Can we use the relationship at smaller scales?

We compared independent estimates of total root carbon allocation (TRCA) and fine root net primary production (NPPfr) for temperate forests to total root carbon allocation (TRCA-RN) estimates derived from an empirical model developed by J. W. Raich and K. J. Nadelhoffer for world forests. Measured total root carbon allocation for temperate forests ranged from 233 to 1013 g C . m(-2). yr(-1) and was not correlated to TRCA calculated from the Raich and Nadelhoffer model for world forests. Fine root NPP was not correlated to TRCA-RN; however, a strong correlation was found between NPPfr and TRCA-RN for five control Pinus resinosa natural forests and plantations. The poor correlation between measured TRCA or NPPfr and the estimates may be due to interspecies differences in belowground carbon allocation, variation in foliage:root carbon allocation ratios due to water and nutrient availability, and violations in the carbon budget approach. Using the Raich and Nadelhoffer model to estimate total root carbon allocation and to construct stand carbon budgets for a stand is not an acceptable substitute for measuring soil carbon fluxes.